But the hw_timer isr is also called without being armed by my own code, approximately every 800ms.
I searched through the esp8266 arduino library but I can't find any code which is using timer1 except for Tone.cpp core_esp8266_waveform.cpp. I also red that PWM is using timer1. But none of these am I using in my code.
How can I find out what is arming the timer1?